


I'll Keep You

by sherlockian4evr



Category: Sherlock (TV)
Genre: Anal Sex, Dubious Consent, Incubus!John, John Watson Has a Large Cock, M/M, Virgin Sherlock, enormous, halloween fic
Language: English
Status: Completed
Published: 2017-11-08
Updated: 2017-11-08
Packaged: 2019-01-30 22:27:56
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,335
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12662712
Author URL: https://archiveofourown.org/users/sherlockian4evr/pseuds/sherlockian4evr
Summary: Sherlock is jealous of John's dates, but he also knows something's not quite right. He figures out John is an incubus and wonders why John hasn't tried to get a leg over with him.Beta read bySherlock1110.





	I'll Keep You

John returned to the flat, the glow of another conquest shining bright about him. Sherlock rolled his eyes and threw himself down on the sofa. "Enjoyed yourself, then," the detective said, his voice full of snark to hide his hurt..

The doctor smiled benignly at his friend. Sherlock looked so fragile laying there on the sofa in his pyjama bottoms, T-shirt and dressing gown. He licked his lips, then made himself look away from the tempting sight. "Yes, I did." He whistled as he walked into the kitchen and put on the kettle.

"What is that, your third this month?" The detective punched the Union Jack pillow, then flipped around so his head was at the other end of the sofa. "Doesn't it get boring?"

John laughed to himself at his virginal flatmate's naive point of view. "Five and no." It never got boring. Women. Men. Fucking them was what he lived for. In fact, fucking them gave him the energy to keep on living and had done for far longer than he could remember. He fixed two cups of tea, carrying one through to set on the coffee table by Sherlock's head. He bit his lip as he noticed how his friend's dressing gown draped over his slim, nymph like form and started planning his next sexual encounter as a distraction. There was that ginger he'd met at Tesco's. His phone number was already burning a hole in John's pocket. "I think I'll turn in for the night. Try to get some sleep."

Sherlock only grunted. He lay there, silently, until he heard the upstairs door click shut, then he sprang up and opened his laptop. He was going to continue his research. There was something off about John. He pulled people entirely too easily and why wasn't he interested in Sherlock? The detective was sure he had given off all the correct signals. John should have shown an interest in him by now.

After several hours, Sherlock had his answer. At first, he dismissed it as impossible, but then he reminded himself of the difference between impossible and improbable using his own mantra. John was a 'fuck demon', an incubus, to be precise. He had first appeared in Africa centuries ago using the name Hagesh along with his sister, Harrel. They had moved steadily north, through the Middle East and up into Europe, dissapearing in the late 1800s. According to lore, the incubus Hagesh not only craved sexual release, but required it to maintain life.

The detective slammed his laptop shut. He loved John. He would happily sleep with him. Why hadn't the incubus seduced him? He looked in the direction of John's bedroom, his heart racing. Enough was enough. He would make the incubus want him... one way or another.

* * *

The next crime scene provided just the chance Sherlock needed. As soon as they entered the house, he swept off his Belstaff and handed it to John. After that, he found every reason to crawl about the floor and waggle his plush arse in the air. He flashed it in John's direction, but he didn't stop there. He made sure Lestrade got an eyeful. From the look on the DI's face it certainly was appreciated. The problem was, it was John he wanted to affect.

Sherlock leapt to his feet and moved close to Greg... a bit too close. He was determined to make John react even if he had to make him jealous to do it. He licked his lips as he let his eyes drop to the DI's mouth, then he started making his deductions. Gratifyingly, Greg's pupils blew wide and he wrapped his coat around himself as if to hide something. Sherlock grinned and made a point of not looking at John.

As soon as the detective had explained everything, John cleared his throat. "Amazing." He handed Sherlock his coat, stepping between the detective and Lestrade. "Sorry, Greg, but we really have to be going. Sherlock can come by tomorrow with his statement." John grabbed his flatmate by the arm and dragged him from the house.

"What has got into you?" John demanded as the detective hailed a cab.

Sherlock sniffed. "I don't know what you're talking about."

"Oh, I think you do," the doctor growled.

Just then, a cab pulled up. As per usual, Sherlock opened the cab door and held it open for John, his expression bland. The incubus climbed in, and slid across the back seat. He clenched his left hand into a fist and tried to ignore it when the detective sat just a bit too close to him. Their thighs were almost touching and John could smell the unique fragrance that was Sherlock - tea, formaldehyde, resin and that special something that smelled uniquely of the untouched virgin. It was all John could do to stop the transformation from his human disguise to his true incubus form. He bit the edge of his hand and thought of someything else, a rotting corpse, anything. At the next traffic light, he bolted from the car and walked the rest of the way back to Baker Street.

* * *

When John got back to the flat, it was to find Sherlock perched on the back of his chair. The detective had shed both coat and jacket and had rolled both shirt sleeves up to his elbows. The top two buttons of his shirt were unfastened, revealing the base of his throat and a hint of his chest. The moment the doctor entered the room, Sherlock hopped down from the chair and approached him seductively.

"Sherlock, stop this. You don't know what you're doing," John warned, his hands fisted at his sides. He wanted the detective almost too much to bear. He couldn't take too much more temptation.

Sherlock didn't stop. He moved right up into John's personal space until they were breathing the same air. "I know what I'm doing. I know what you are. You're an incubus, John. I want to have sex with you."

The incubus trembled with the effort of not moving, not transforming. "You don't know anything about what that means." He breathed in Sherlock's scent. "You're a virgin. I don't want to break you. The things I would do to you..."

"Do them. Break me."

Sherlock kissed John on the lips. It was an innocent kiss, closed mouthed and chaste. Still, the incubus shuddered. He pushed the detective away, trying to get hold of himself, but it was no use. John couldn't stop the transformation this time, he wanted Sherlock too much. He had to have him. His body shifted. His horns appeared first, small nubs that grew into two great, black and silver spirals atop his head. The illusion of clothing fell away and next to appear was his great tail that whipped about and curled around his right leg as it finally came to rest.

For all of his friend's transformations, it was John's cock that held Sherlock's attention. It was massive, as thick as the detective's forearm, and flushed a deep dark purple. It was also ridged and covered with bumps, unlike anything Sherlock had ever imagined. He swallowed hard and backed up a step, suddenly afraid that he couldn't give John what he needed. No, he knew he couldn't, it would surely kill him, wouldn't it?

The detective stumbled backwards a couple of steps, but John lunged for him. He wrapped his arms around Sherlock, his arms enfolding him and helping to hold him in place. It wasn't just his form that had changed, but his whole demeanour. "You've fucking teased me too much. I'll have you, if that's what you want." He used his left hand to rip the buttons from Sherlock's too tight shirt. John licked along the detective's chest and up to his throat, stopping over his pulse point to feel the beat of his prey's racing heart. "There's no need to be afraid, my darling. I'll take you. I'll make you scream my name. I'll wring you dry. But there will be enough of you left to beg me for more."

Sherlock brought his hands up and grasped the incubus' arms. "John! What..."

John smashed their lips together, forcing his tongue into the detective's mouth. He plundered it thoroughly, exploring every nook and cranny. When he broke the kiss, Sherlock was a gasping, limp form in his arms. The incubus worked his way along Sherlock's jawline and down his neck, kissing and sucking, leaving a trail of little bruises in his wake. When he reached the detective's shoulder, he bit him, special teeth injecting a chemical that would help to relax Sherlock's muscles and open him up. He licked over the puncture marks, closing the wound. The entire time, the detective moaned with pleasure in his arms. "Like that, do you?" His tail wrapped around Sherlock's waist.

"Mm, hurts. Feels good." Sherlock's head fell back in a silent entreary for more. Interesting.

"My little pain slut. I can give you more." He scooped up Sherlock, his slim body easy to carry, and took him through to the detective's bedroom where he threw him down on the bed. John quickly divested the slightly disoriented Sherlock of his clothes, then climbed atop him. "Now, where was I?" The incubus leaned down and bit the detective's shoulder just hard enough to make him cry out. "Such lovely sounds, my little slut, but let's see if I can get them a different way." He moved between Sherlock's thighs and ran a hand over the detective's bollocks, then over his perenium and finally to his hole. "I can't wait to be inside this."

The detective's heart skipped a beat at the thought of John's monstrous cock inside him. He tried to sit up. "I can't, John. Please. It would kill me!"

The incubus lunged forward and swallowed the rest of Sherlock's protest in a kiss. "Oh, my beautiful little boy, you can take me, I assure you." He took one of the detective's hands and rested it on his own hugh cock. "Feel it, Sherlock. You were meant for this. You were meant to take me." He bit down on Sherlock's shoulder again, injecting another round of chemicals into his system, then licked that wound closed as well. "But if you want to take me, you have to let me inside." John's fingers were proding at the detective's entrance again. "Relax and let me in, my little slut. Do it. You owe it to me after the way you displayed yourself in front of Greg."

Sherlock spread his thighs wide for John and moaned when the incubus breached him with unlubed fingers. It felt strange, wrong somehow, but right and it burned. It felt wonderful. "Jooohn," he moaned, his head rocking back and forth on the pillow.

"This is mine," John hissed as he added another finger. The chemicals he had introduced to his little painslut's body were already working to make him loose. He fucked his fingers into him brutally, adding finger after finger until he was almost fucking him with his entire hand.

"John, John, too much, John." Sherlock's body rocked with the force that the incubus was using to prepare him. He felt like he was being split open already and this was nothing. Nothing! His heart was racing with trepidation, but his cock was rock hard and aching.

"So fucking beautiful," John breathed as he lined his cock up with Sherlock's hole. "Brace yourself, little one." He pushed into the detective's body, relishing the incredibly tight, virginal heat that surrounded him.

Sherlock cried out, wailing "God, I can't. It's too much." His back arched and tears slid down his face. "I's too big, John." He clawed at the incubus' back ineffectually.

"No, Sherlock. You were born to take me." He shoved in deeper. "Look at how you cry and sob at taking my monster cock. No one else has made it this far." He pulled back and thrust forward, going even deeper. "No one else has ever given me such magnificent pleasure. "Don't worry. I will make sure you take all. Of. Me." With one more thrust, he drove all the way in.

Sherlock bucked and writhed as he felt himself spitted. He was touched in places he never had been before. Lights sparked behind his eyes as John began to move, fucking him in earnest and stroking over his prostate with firm, insistent strokes. He was caught in a place where pain and pleasure became one and it all belonged to "Joooohn!"

John rocked into him, feeling a possessive pleasure flow through him. "Such a little slut, all the time putting your tight ripe body out there in those tight little trousers of yours. Who do you belong to?"

Sherlock cried out, "You, John!"

The incubus reached between them and grasped Sherlock's cock. He pumped it with firm strokes as he thrust into the detective's lithe body. Soon, Sherlock came, spilling his seed over John's hand and calling his name in great gasping cries. John fucked him through his orgasm, chasing his own release which soon followed. He drove into the detective one last time filling him with his release, then he collapsed on Sherlock who had passed out beneath him.

* * *

When Sherlock woke up, John had transformed back to his human appearance. He had a glass of water and some paracetamol that he pressed on the detective. “How do you feel, babe?”

Sherlock sat up and winced. "Sore." He swallowed the tablets and looked shyly at his flatmate. "But good." He blushed bright red, all the way to his ear tips.

John leaned forward and brushed their lips together tenderly. "So, are you mine? Or are you going to run screaming?"

Biting his lip, Sherlock looked at his friend shyly. "I'm yours, if you'll have me and quit chasing those men and women."

John's eyes glinted. "Oh, pretty little boy, I'll have you." He kissed Sherlock, tangling his fingers in his hair. "And I'll keep you."

**Author's Note:**

> I read and treasure every single comment I receive, but I'm totally crap at responding to them. Please know that they fuel me. Thank you in advance.
> 
> If you want to podfic or translate this or create a drawing based on it, go for it. Just please let me know and link back to my fic.
> 
> Follow me on [Tumblr](http://shippingintothenight.tumblr.com) or @sherlockian4evr on Twitter.
> 
> Find out how my muse is doing at [My Other Tumblr](http://sherlockian4evr-status.tumblr.com).


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